Radiotelephony



F. M. DOOLITTLE RADIOTELEPHONY Nuv. 4 1924. 1,513,973

Filed Feb. 21, 1924 Receuvung Apparatus Reach/Lug Ap m-ratus reproduction of performances Patented Nov. 4, 1924.

PATENT v OFF-ICE.

FRANKLIN M. DOOLIT'ILE, OF NEW HAVEN, CONNECTICUT.

RADIOTELEPHONY.

Application filed February 21, 1924. Serial No. 694,388.

To all whom-it may concern:

Be it known that I, FRANKLIN M. Doo- LITTLE, a citizen of the United States, residing at New Haven, in the county of New Haven and State of Connecticut, have invented a new and useful Improvement in Radiotelephony; and I do hereby declare the following, when taken in connection with the accompanying drawings and the characters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this application, and represent diagrammatically one form which an apparatus for practicing my invention may assume.

This I invention relates to a method of transmitting and receiving radio telephonic impulses in such a manner as to evoke in the mind of the listener substantially the same consciousness of location of the source of the sound or sounds as he would have obtained had hebeen personally present at the transmitting station.- An important application of, my invention is to the field of radio telephone broadcasting, the end in view being-to place the listener to a broadcasting program in the same acoustical relation with the performance as though he were present.

In the present broadcasting of entertainment and other matter by radio, use is made of some form of microphone pickup device which respoyds with approximate equality to a wide range of frequencies and the circuits and apparatuses employed areso designed and organized that the waves radiated convey a very exact impression as to the true tone values to a listener with suitable receiving equipment for detecting them. There is one serious defect in the broadcast by radio in this way for, however true the tones themselves may be to the original ones, the listener is deprived of that consciousness of location of. the performer or performers which he would have were he present in person at the performance and hence the rendition is distorted andunnatural.

The purpose of my invention is to eliminate the unnaturalness above described and to this end a method and apparatus -are emloyed for transmitting and receiving by radio el ph ny, t only t e toneswhichat the performance is connected.

are produced at a performance of whatever character or description, but those slight differences in time of arrival of the sound at the two ears which the mind translates into impressions of location. By means of my invention a radio listener can have presented to his ears at a distant point a performance which simulates the original in all essential particulars.

My invention takes advantage of the auditory principle referred towvith the end in view of providing a methifd of and ap paratus for transmitting and receiving the phase differences in the arrival of sounds at the ears ofalistener present at the performance to a distant point by radio so that the radio listener may obtain the same acoustical impression as to the location of the source of the sound or sounds as though he too were present. To this end I employ two separate channels of, radio transmission which may be obtained in a variety of ways as, for example, by the use of two wave lengths or by employing a single .wave length modulated at two superaudible"frequencies which are in turn modulated by the voice frequencies, two microphonic devices of suitable construction separated by substantially the ears tion of one channel and the other that of the other channel so that two versions 0 the same sound or sounds differing in the necessary phase relation, produce the consciousness of location when interpreted by the mind of the listener.

I also employ two radio receivers for the simultaneous reception on the two channels bearing the phase differentiated versions of the performance. My invention further consists in employing two telephone listening devices the right one of which is con neoted to the receiver associated with the channel with which the right microphone at the performance is connected and the left one with the receiver associated with the channel to which the left microphone arrangement the right receiver produces an essential duplication of the vibrations reachof a human being, one of which is arranged to modulate the radia- VVith this ing the right microphone and the left reeeiver of those reaching the left microphone in their relative phase-relations as well as in true tone-values. Hence, the ears of thelistener are in effect transferred to the location of the microphones. Ifa telephone v headsetis employed and the left receiver is associated with the right microphone and the right receiver associated with the left microphone the impression of location will be reversed, objects on the left appearing to be on the right and vice versa. Since the location impression has been found tov be due to the phase relatlon in the arriving of sounds at the. two ears and is not dependent on the relative intensities of the sounds received by both ears considerable variation in the signal strength in the two channels be permitted without appreciably impairing the impression of location.

My invention will be understood by referring to theaccompanying drawing, which diagrammatically represents one form which an apparatus for practicing my invention may assume, on which 10, 11, 12 and 13 represent four different sources of sound, such as a quartet of singers. Within the sound range of the sources of sound so des-' ignated I locate two microphones 14 and 15 of any suitable type and preferably separatedjfrom each other by a distance corresponding to that separating the ears of the average individual, but this is not imperative, since the distance of the separation of these microphones may be varied according to circumstances, without departing from my improved method. Themicrophone 14 forms a feature of an independent radio transmitting apparatus,,generally designated by '1, while the microphone 15 forms a feature of another radio transmitting pparatus generally designated by T Each transmitting apparatus just described has the usual antennae 16 and the usual ground connection 17. The apparatus above described, it will be understood, is located at the broadcasting 'station. At the receivingstation I locate two receiving apparatuses R and R each independent of the other, each having the usual antennae 18 and the usual ground connection 19, and respectively provided with telephone receivers 20 and 21,

adapted in any convenient manner to be fittedto the ears of the person who wishes to listen in. The transmitting apparatus T and the receiving apparatus R are'tuned in consonance, while the transmitting a para; tus T and the receiving apparatus 2 are tuned in consonance. Whether the tuning described is effected by wave lengths or by employing the same wave length modulated at two superaudible frequencies which are in turn modulated to the voice frequencies. at the receiving station, they will remain distinct in the sense of providing two distinct, non-interfering channels of radio communication. if the receiving apparatus B should be tuned to.

differentiating the of sound 12 and 13 would seemingly exchange places with the sources of sound 10 and 11 and vice versa, which would not,

however, affect the ability of the apparatus to evoke mental impressions of location in the mind of the listener.

in the use of the apparatus, the person listening -innot only receives the tone values as in ordinary radio reception, but also receives a mental picture of the respective positions of the different sources of sound at'the sending station, whether those sources of sound be persons singing or the pieces of an orchestra, and-so on.

I claim: I r

1. In an apparatus for transmitting sounds by radio telephony, the combination ,with two sound pick-up devices so relatively positioned as to receive sound in a manner simulating the reception of sounds by the ears of a human being; of two non-interfering channels of radio transmission respectively connected with the said pick-up devices.

2. In an apparatus for receiving sounds by radio telephony, the combination with two listening devices, one for'each ear; of a double-channel radio telephone receiver for the'simultaneous and non-interfering reception of two versions of the same sound, the respective channels of the said double channel radio receiver being connected with the respective listening devices.

3. In an apparatus for transmitting and receiving sounds by radio telephony, the combination of two sound pick-'up devices relatively positioned so .asto receive sound in a manner simulating the reception of sounds by the ears of a human being; of two independent, non-interfering radio transmit; ting apparatuses connected with the -respec tive-sound. pick-up devices, a double-channel radio telephone receiver for .the simultaneous .and non-interfering reception of the two versions of the same'sound which have been picked up by the saidsound pick-up devices, and two'listening devices, one for each ear, respectively connected with the respective channelsof the said double-channelradio telephone receiver.

4. A method-of transmitting and -receivmmun cation and converging the sounds so transmitted upon the respective ears of the specification in the presence of two subscriblistener, whereby there is evoked in his mind ing witnesses.

location of the origin of the various sounds substantially the same consciousness of the FRANKLIN DOOLITTLE.

5 as would be actually apparentto a person Witnesses:

located at the scene of their origin. Fnnnnmo C. EABLE,

In testimony whereof, I have signed this MALCOLM 1. NICHOLS. 

